The innate immune system coordinates the inflammatory response to pathogens by a system that discriminates between self and non-self via receptors that identify classes of molecules synthesized exclusively by microbes. These classes are sometimes referred to as pathogen associated molecular patterns (PAMPs) and include, for example, lipopolysaccharide (LPS), peptidoglycans, lipotechoic acids, and bacterial lipoproteins (BLPs).
LPS, an abundant outer cell-wall constituent from gram-negative bacteria, is recognized by the innate immune system. Although the chemical structure of LPS has been known for some time, the molecular basis of recognition of LPS by serum proteins and/or cells is only now being elucidated. In a series of recent reports, a family of receptors, referred to as Toll-like receptors (TLRs), have been linked to the potent innate immune response to LPS and other microbial components. TLR are membrane proteins having a single transmembrane domain. The cytoplasmic domains are approximately 200 amino acids and share similarity with the cytoplasmic domain of the IL-1 receptor. The extracellular domains are relatively large (about 550-980 amino acids) and may contain multiple ligand-binding sites.
The importance of TLRs in the immune response to LPS has been specifically demonstrated for at least two Toll-like receptors, Tlr2 and Tlr4. For example, transfection studies with embryonic kidney cells revealed that human Tlr2 was sufficient to confer responsiveness to LPS (Yang et al., Nature 395:284-288 (1998); Kirschning et al. J Exp Med. 11:2091-97 (1998)). A strong response by LPS appeared to require both the LPS-binding protein (LBP) and CD14, which binds LPS with high affinity. Direct binding of LPS to Tlr2 was observed at a relatively low affinity, suggesting that accessory proteins may facilitate binding and/or activation of Tlr2 by LPS in vivo.
The importance of Tlr4 in the immune response to LPS was demonstrated in conjunction with positional cloning in lps mutant mouse strains. Two mutant alleles of the mouse lps gene have been identified, a semidominant allele that arose in the C3H/HeJ strain and a second, recessive allele that is present in the C57BL/10ScN and C57BL/10ScCr strains. Mice that are homozygous for mutant alleles of lps are sensitive to infection by Gram-negative bacteria and are resistant to LPS-induced septic shock. The lps locus from these strains was cloned and it was demonstrated that the mutations altered the mouse Tlr4 gene in both instances (Portorak et al., Science 282:2085-2088 (1998); Qureshi et al., J Exp Med 4:615-625 (1999)). It was concluded from these reports that Tlr4 was required for a response to LPS.
The biologically active endotoxic sub-structural moiety of LPS is lipid-A, a phosphorylated, multiply fatty-acid-acylated glucosamine disaccharide that serves to anchor the entire structure in the outer membrane of Gram-negative bacteria. We previously reported that the toxic effects of lipid A could be ameliorated by selective chemical modification of lipid A to produce monophosphoryl lipid A compounds (MPL® immunostimulant; Corixa Corporation; Seattle, Wash.). Methods of making and using MPL® immunostimulant, and structurally like compounds, for vaccine adjuvant and other applications have been described (see, for example, U.S. Pat. Nos. 4,436,727; 4,877,611; 4,866,034 and 4,912,094; 4,987,237; Johnson et al., J Med Chem 42:4640-4649 (1999); Ulrich and Myers, in Vaccine Design: The Subunit and Adjuvant Approach; Powell and Newman, Eds.; Plenum: New York, 495-524, 1995). In particular, these and other references demonstrated that MPL® immunostimulant and related compounds had significant adjuvant activities for enhancing humoral and/or cell-mediated immunity to the antigens, when used in vaccine formulations with protein and carbohydrate antigens.
Synthetic mono- and disaccharide molecules which share structural similarities with MPL® immunostimulant, referred to as aminoalkyl glucosaminide phosphates (AGPs), have been described, see for example, U.S. Pat. No. 6,113,918, U.S. Pat. No. 6,303,347, and WO 98/50399, published Oct. 12, 1998. These compounds retain significant adjuvant characteristics when formulated with antigens in vaccine compositions and have similar or improved toxicity profiles when compared with monophosphoryl lipid A. These compounds have been described for use in combination with antigens in vaccine formulations (U.S. Pat. No. 6,113,918) and in the absence of antigen, as monotherapies, WO 01/90129, published Nov. 29, 2001.
Cyclic aminoalkyl glucosaminide phosphates or “cyclic AGPs” have been described in PCT Patent Application No. PCT/US01/24284. These cyclic AGPs are effective immunoeffector molecules which enhance humoral and cell-mediated immune responses to vaccine antigens. As used herein, the term “cyclic AGP” means an azacycloalkyl or (azacycloalkyl)alkyl glucosaminide phosphate, wherein a 2-deoxy-2-amino-b-D-glucopyranose (glucosamine) is glycosidically linked to an azacycloalkyl or (azacycloalkyl)alkyl (aglycon) group.
The present invention provides monotherapies formulated and administered in the absence of exogenous antigens for the prophylactic and/or therapeutic treatment of plant and animal diseases and conditions, such as infectious diseases, autoimmunity and allergies. The monotherapies of the present invention comprise one or more cyclic AGPs. These and other aspects of the invention will become evident upon reference to the following detailed description and the attached drawings.